This proposed project will try to determine if the cell mediated immune response plays a role in the pathogenesis and perpetuation of recurrent aphthous stomatitis (RAU). The project will employ both clinical and (clinical pathology) laboratory examinations. The practicing dentist and physician has for years found the clinical management of patients with recurrent aphthous stomatitis to be an enigma. The problem is one which is complicated by unknown etiology, lack of adequate chemotherapy and the recurrent complaints from and discomforts to the patient. Recent research has revealed the strong possibility that immunologic parameters play a major role in the pathogenesis of this disease. The hypothesis that some T-cell functions are involved in the etiology of this clinical disease is the basis of our proposed investigation. Our objectives are: 1) To determine the clinical diagnosis of patients with RAU and support this with histopathologic findings, and 2) to examine the cell-mediated immune response in patients with RAU and attempt to correlate findings with the pathogenesis of the clinical disease. Approximately 200 subjects with Rau will be evaluated in the proposed study. Evaluation will include: thorough subjective medical history, oral examination, a questionnaire "Recurrent Aphthous Stomatitis -- patient profile," and clinical laboratory examinations (CBC, Cytologic smear, cultures for Herpes virus, Herpes neutralizing antibody study, Lymphocyte transformation study, Human Leukocyte Migration Inhibition, Rosette-forming cell test and a skin test battery testing for cutaneous hypersensitivity to Candida, Coccidioides, Mumps, PPD, Streptokinase/Streptodornase, and Tricophytin).